1. Introduction : Phosphorus (P) is one of the critical nutrient elements after nitrogen for increasing crop growth and yield. The Phosphatic fertilizers of higher water solubility are required for alkaline soils and produced by acidulation of rock phosphate with sulphuric acid or phosphoric acid. Phosphorus adsorption behavior has been frequently used to characterize P supplying capacity of soils. This is because adsorbed phosphate equilibrates with P in soil solution, there by, maintaining adequate P supply to plants throughout the growth cycle. Methodology A long-term fertilizer experiment under rice-wheat crop rotation is in progress on Typic Haplustept soil at research farm, Department of Soil Science, Punjab Agricultural University, Ludhiana, since 1999. The site is located in the Indo-Gangetic alluvial tract at 30 56’ N 75 52’E and at an attitude of 274 m above mean sea level. The effects of inorganic and integrated fertilizers was studied through nine treatments comprises T 1 :100%N, T 2 : 100%NP, T 3 :100%NPK, T 4 :100%NPK+(P to wheat), T 5 :150%NPK, T 6 :100% NPK+FYM, T 7 : 100%NPK+GM, T 8 :100%NPK+straw incorporation and in addition to an absolute T 9 : control. The surface (0-15 cm) soil samples were collected after harvesting of wheat during 2012-2013. The soil samples were analyzed for adsorption- desorption behavior using the scheme described by (Murphy and Riley 1972) and (Singh and Jones 1976). Methodology A long-term fertilizer experiment under rice-wheat crop rotation is in progress on Typic Haplustept soil at research farm, Department of Soil Science, Punjab Agricultural University, Ludhiana, since 1999. The site is located in the Indo-Gangetic alluvial tract at 30 56’ N 75 52’E and at an attitude of 274 m above mean sea level. The effects of inorganic and integrated fertilizers was studied through nine treatments comprises T 1 :100%N, T 2 : 100%NP, T 3 :100%NPK, T 4 :100%NPK+(P to wheat), T 5 :150%NPK, T 6 :100% NPK+FYM, T 7 : 100%NPK+GM, T 8 :100%NPK+straw incorporation and in addition to an absolute T 9 : control. The surface (0-15 cm) soil samples were collected after harvesting of wheat during 2012-2013. The soil samples were analyzed for adsorption- desorption behavior using the scheme described by (Murphy and Riley 1972) and (Singh and Jones 1976). Objective To study the dynamics of soil phosphorus adsorption and desorption behavior under continuous application of inorganic and integrated fertilization. Objective To study the dynamics of soil phosphorus adsorption and desorption behavior under continuous application of inorganic and integrated fertilization. ADSORPTION-DESORPTION OF PHOSPHORUS IN SOIL RECEIVING LONG-TERM FERTILIZER, MANURE AND CROP RESIDUE Sukhvir Kaur 1, G S Dheri 2, B S Brar 2 and R S Gill 3 Department of Soil Science Punjab Agricultural University, Ludhiana-141004 (sukhskydiver88@yahoo.com ) References :Singh R and Bahaman P C (1976) Transformation of P in acid soil under water logged and upland soils. J Indian Soc Soil Sci 24:171-74. Murphy J and Riley J P (1972) A modified single solution method for determination of phosphate in natural water. Anal Chem Acta 27:31-36. Conclusion The results showed that the amount of P adsorption increased with increase in the amount of P added irresespective of the fertilizer treatment. However, per cent P adsorption decreased gradually with increasing level of added P, However in desorption per cent increased with increasing level of added P. Phosphorus adsorption decreased with the application of integrated fertilizer application as compared to inorganic fertilizers, thereby indicating a favourable effect on P availability in the soil. Conclusion The results showed that the amount of P adsorption increased with increase in the amount of P added irresespective of the fertilizer treatment. However, per cent P adsorption decreased gradually with increasing level of added P, However in desorption per cent increased with increasing level of added P. Phosphorus adsorption decreased with the application of integrated fertilizer application as compared to inorganic fertilizers, thereby indicating a favourable effect on P availability in the soil. Key Results The adsorption of P varied between 21.7 to 187.4, 19.7 to 140.6, 18.9 to 130.6, 20.9 to 158.2, 17.8 to 122.1, 15.1 to 94.2, 16.2 to 106.0, 17.1 to 112.9, 22.8 to 201.3 mg P kg -1 soil with an application of graded levels of P (25 to 800 mg P kg -1 soil) for the T 1, T 2, T 3, T 4, T 5, T 6, T 7, T 8 and T 9 treatment, respectively. The adsorption of P increased with an increase in the amount of added P, however, the percent of P adsorption decreased gradually with increasing levels of added P. The maximum value of Langmuir adsorption maxima (b=222.2 mg P kg -1 ) and bonding energy constant (k=1.68 L mg -1 ) was reported in control whereas, the minimum value of ‘b’ (108.7 mg P kg -1 ) and ‘k’ (1.00 L mg -1 ) was observed in 100%NPK+ FYM treatment. The desorption of P varied between 0.19 to 8.31, 0.41 to 19.97, 0.62 to 21.90, 0.36 to 16.46, 0.73 to 26.88, 0.91 to 39.78, 0.82 to 33.29, 0.79 to 29.25 and 0.16 to 7.25 mg P kg -1 soil with an application of graded levels of P (25 to 800 mg P kg -1 soil) for the T 1, T 2, T 3, T 4, T 5, T 6, T 7, T 8 and T 9 treatment, respectively. The desorption of P increased with the increase in amount of fertilizer P added. The value of Freundlich constant ‘a’ was maximum in control (4.01 mg P kg -1 ) and decreased with fertilizer applications. The value of ‘a’ and ‘n’ was minimum under balanced integrated fertilization applications. Desorption of added P improved under the long-term application of balanced fertilizer and integrated use of organic manure and fertilizers. Key Results The adsorption of P varied between 21.7 to 187.4, 19.7 to 140.6, 18.9 to 130.6, 20.9 to 158.2, 17.8 to 122.1, 15.1 to 94.2, 16.2 to 106.0, 17.1 to 112.9, 22.8 to 201.3 mg P kg -1 soil with an application of graded levels of P (25 to 800 mg P kg -1 soil) for the T 1, T 2, T 3, T 4, T 5, T 6, T 7, T 8 and T 9 treatment, respectively. The adsorption of P increased with an increase in the amount of added P, however, the percent of P adsorption decreased gradually with increasing levels of added P. The maximum value of Langmuir adsorption maxima (b=222.2 mg P kg -1 ) and bonding energy constant (k=1.68 L mg -1 ) was reported in control whereas, the minimum value of ‘b’ (108.7 mg P kg -1 ) and ‘k’ (1.00 L mg -1 ) was observed in 100%NPK+ FYM treatment. The desorption of P varied between 0.19 to 8.31, 0.41 to 19.97, 0.62 to 21.90, 0.36 to 16.46, 0.73 to 26.88, 0.91 to 39.78, 0.82 to 33.29, 0.79 to 29.25 and 0.16 to 7.25 mg P kg -1 soil with an application of graded levels of P (25 to 800 mg P kg -1 soil) for the T 1, T 2, T 3, T 4, T 5, T 6, T 7, T 8 and T 9 treatment, respectively. The desorption of P increased with the increase in amount of fertilizer P added. The value of Freundlich constant ‘a’ was maximum in control (4.01 mg P kg -1 ) and decreased with fertilizer applications. The value of ‘a’ and ‘n’ was minimum under balanced integrated fertilization applications. Desorption of added P improved under the long-term application of balanced fertilizer and integrated use of organic manure and fertilizers. Table: Amount of P adsorbed (mg P kg -1 soil) in different soil (under long-term differention) treated with various P levels TreatmentsP added (mg P kg-1 soil) 2550100200400600800 100%N21.735.463.9107.6167.7186.4187.4 100%NP19.731.154.688.9130.5137.4140.6 100%NPK18.929.651.583.7122.4128.4130.6 100%NPK (P to wheat) 20.933.358.797.2143.4153.0158.2 150%NPK17.827.848.075.9112.0117.6122.1 100%+FYM15.122.136.057.288.797.494.2 100%NPK+GM16.225.040.062.6100.0103.8106.0 100%NPK+ straw incorporation 17.126.143.769.0105.6109.4112.9 Control22.836.465.7113.0183.4199.9201.3 Table: Amount of P desorbed (mg P kg -1 soil) in different soils under long-term differential fertilization treated with various P levels Treatments P added (mg P kg-1 soil) 2550100200400600800 100%N 0.190.391.032.174.076.118.31 100%NP 0.410.841.984.108.1114.519.9 100%NPK 0.621.052.425.2910.616.221.9 100%NPK (P to wheat) 0.360.731.763.796.4611.916.4 150%NPK 0.731.342.796.4612.719.926.8 100%+FYM 0.911.604.108.5621.129.239.7 100%NPK+GM 0.821.563.487.2717.024.133.2 100%NPK+ straw incorporation 0.791.483.197.1815.121.729.2 Control 0.160.320.861.853.625.327.25 Table: Sorption of P as affected by long-term use of inorganic and integrated fertilizer Equilibrium solution P concentration (mg P kg -1 )